This is a previously reported problem (TTSD-16799) that has usually been resolved with the current Service Packs.The problem was reported with Tekla Structures 2017i SP4. The following ServicePack fix the problem: 2018 SP1, 2017 SP8, 2017i SPnext, 2016i SPnextMake sure that you have installed the latest ServicePack for each version of Tekla Structures.